Description

In the Linux kernel, the following vulnerability has been resolved: soundwire: bus: Fix unbalanced pm_runtime_put() causing usage count underflow This reverts commit 443a98e649b4 ("soundwire: bus: use pm_runtime_resume_and_get()") Change calls to pm_runtime_resume_and_get() back to pm_runtime_get_sync(). This fixes a usage count underrun caused by doing a pm_runtime_put() even though pm_runtime_resume_and_get() returned an error. The three affected functions ignore -EACCES error from trying to get pm_runtime, and carry on, including a put at the end of the function. But pm_runtime_resume_and_get() does not increment the usage count if it returns an error. So in the -EACCES case you must not call pm_runtime_put(). The documentation for pm_runtime_get_sync() says: "Consider using pm_runtime_resume_and_get() ... as this is likely to result in cleaner code." In this case I don't think it results in cleaner code because the pm_runtime_put() at the end of the function would have to be conditional on the return value from pm_runtime_resume_and_get() at the top of the function. pm_runtime_get_sync() doesn't have this problem because it always increments the count, so always needs a put. The code can just flow through and do the pm_runtime_put() unconditionally.

References 3

• git.kernel.org https://git.kernel.org/stable/c/203aa4374c433159f163acde2d0bd4118f23bbaf
• git.kernel.org https://git.kernel.org/stable/c/4e5e9da139c007dfc397a159093b4c4187ee67fa
• git.kernel.org https://git.kernel.org/stable/c/e9537962519e88969f5f69cd0571eb4f6984403c

Remediation